From prior art, a head restraint for a seat in a motor vehicle is known which comprises an essentially cylindrical support body. The longitudinal axis of the support body is aligned horizontally and is arranged parallel to the upper edge of the seat back.
The support body is kept in position in respect of the seat back by means of one or two guide rods protruding vertically from the upper edge of the seat back; the said guide rods engage the lower side of the support body. Anchoring of the upper ends of the guide rods in the cylindrical support body is designed in such a way as to allow inclination of the support body in, or opposed to, the direction of travel. The guide rods can be lowered into the seat back or they can be partly pulled out from the seat back, thereby providing height adjustability of the support body.
Such a head restraint has numerous disadvantages.
It is particularly disadvantageous that the neck/head region is neglected from an orthopaedic point of view. If the vehicle is brought to an abrupt halt, for example by a frontal obstruction, there is a whiplash-like swinging of the head or the torso, in longitudinal direction of the vehicle. At the end of the backward whiplash-movement, the head hits against the support body.
In this, due to a very small impact surface, on the one hand very considerable G-forces impact on the brain, which can lead to cerebral haemorrhages. On the other hand it is frequently observed that during the whiplash-like forward movement, the driver is at least somewhat lifted out of his/her seat. During the whiplash movement directed backward, this results in the cylindrical support body engaging not primarily at the head but too low, at the transition region between head and neck. Consequently, backward overstretching of the neck occurs. The subsequently occurring symptoms are referred to as cervical-spine whiplash trauma.
The use of such a known head restraint causes cervical-spine whiplash trauma even in cases of rear-end collisions onto a stationary vehicle.
If the rear-end collision happens while the head is turned aside, then additionally, pronounced torsional bending of the cervical spine occurs. This regularly causes irreparable damage to the cervical spine.
If the vehicle is hit laterally, for example at a 90.degree. angle, the head will be tossed about by the forces acting upon it.
Since such injuries as a rule are associated with high treatment costs and at least a 2- to 3-week absence from the workplace, they represent a considerable burden on the national economy.
If the passenger is asleep, then his/her head swings about in an uncontrolled fashion, depending on the shaking of the vehicle and the centrifugal forces. At best, this leads to tenseness of the neck muscles which often leads to headaches and thus to premature fatigue as well as a reduced ability to concentrate.
If the cylindrical support body is in the highest position, as is required in the case of a driver of above-average height, this leads to a large-area gap between the upper edge of the seat back and the underside of the support body. This gap is often associated with draught problems.
A further disadvantage of the known head restraints is the lack of comfort which, during long drives irrespective of draught problems and unintentionally acting acceleration forces, causes muscle tenseness in the upper shoulder and neck region, leading to premature fatigue, limited ability to concentrate, or even headaches and cervical migraines.
GB-A 2 246 292 describes a head-support cushion comprising a cloth pulled rearward over the seat back; at the front of this cushion there is a U-shaped element for supporting the back of the head.
Such a headrest has for example the disadvantage of allowing lateral swinging-through of the cervical spine, in particular during a transverse rebound movement of the torso. This lateral swinging-through of the cervical spine very frequently leads to the cervical spine whiplash-trauma (cervical spine syndrome) which is much feared also for economic reasons.
DE-A1-3042802 discloses a support for the back of the head with a horizontally-adjustable head-support surface located at the top. The adjustable head-support surface is connected to the seat frame by way of flexible tubes or by a joint-type mechanism. If substantial forces are encountered, for example forces consistent with bumping the head as a result of an accident, then the adjustable head-support surface is pushed into its rear position. In this case, direct introduction of force into the frame takes place.
Such a head restraint does not counteract any swinging-through of the cervical lordosis or any rebound movement during a bump as a result of an accident.
EP 0113645 describes a head restraint with a hoop in the shape of an inverted U. In the space between the straight sections of the U-shaped loop, a cushion is fixed in a vertically hingeable way. If the head restraint is moved to the upper position, the cushion hangs steeply downwards and rests against the bar-shaped vertical retainers of the head restraint. By contrast, if the head restraint is moved to the lower position, the hingeable cushion rests flat against the upper rim of the seat back.
The swivellable cushion of this head restraint comprises a flat, plane surface and as a result does not counteract any lateral swinging-through of the cervical lordosis during any rebound movement of the torso as a result of a collision.